Work is continuing to determine the effect of nerve growth factor (NGF) on the rate and mode of reinnervation of the canine heart. To date, the chemical and physiological data suggest that at one month NGF treated animals have reinnervated to a greater degree than their untreated counterparts. At three months post denervation the data are equivocal and at six months there is no discernible difference. These data suggest that continued treatment with NGF is probably necessary to maintain the accelerated rate of reinnervation. Current studies consequently involve comparison of reinnervation between denervated control animals and NGF treated denervated animals. After the initial 5-day treatment with NGF, weekly doses of NGF will be administered until the time of sacrifice at one or three months when biochemical and physiological studies to determine the degree of reinnervation will be performed. BIBLIOGRAPHIC REFERENCES: David J. Witzke and Michael P. Kaye: Myocardial ultrastructural changes induced by administration of nerve growth factor. Surgical Forum 27: 295-297, 1976 (abstract). David J. Witzke and Michael P. Kaye: Hypertrophic cardiomyopathy induced by administration of nerve growth factor. Circulation, Vols. 53 & 54, Suppl. II, II-88, October, 1976 (abstract).